Abstract

The structures of four tin silicate, SnO-SiO2, glasses have been studied using pulsed neutron diffraction to investigate the environment of Sn2+. The glass structure is based on a tetrahedral [SiO4] network and we find that the mean Si-O distance increases slightly as SnO is added. The tin atoms have a well-defined environment, indicating that tin takes the role of a conditional glass former for all compositions. The predominant coordination polyhedron for Sn2+ is a [SnO3] triangular pyramid, although a minority of Sn2+ are in a [SnO4] square pyramid environment. particularly for the higher silica compositions. The majority of the oxygen-oxygen distances in both tin coordination polyhedra are the same as in the [SiO4] tetrahedra. No evidence has been found for a gross change in the short range order with composition which can be associated with a change in the physical properties. (C) 1998 Elsevier Science B.V. All rights reserved.